1. Field of the Invention
The present invention relates to a solid-state imaging apparatus and an imaging system.
2. Description of the Related Art
An imaging system such as a digital camera can be downsized by using a solid-state imaging apparatus in which pixels for imaging each having a photoelectric conversion portion and pixels for focus detection each having a photoelectric conversion portion are arranged on a single substrate. As each pixel for imaging, it is possible to use, for example, a pixel (a red, green, or blue pixel) obtained by forming a red, green, or blue color filter on the photoelectric conversion portion. These pixels for imaging can be arranged in accordance with, for example, a Bayer array, and the pixels for focus detection can be arranged in some of positions where, for example, the red pixels are to be arranged. Focus detection is performed by, for example, a phase difference detection method. The pixel for focus detection adopts a structure for performing pupil division, in which no color filter is normally formed in many cases.
An element isolation region can be formed between the pixels of the substrate so as to prevent crosstalk occurring when a signal charge generated in each pixel moves between adjacent pixels. As the number of pixels increases (as the size of each pixel decreases), however, it has become necessary to increase the photoelectric conversion efficiency of the photoelectric conversion portion and decrease the area of the element isolation region at the same time. This makes it difficult to suppress crosstalk.
In the structure of the above-described pixel array, the amount of crosstalk between, for example, the red pixel and green pixel is different from that of crosstalk between the pixel for focus detection and the green pixel. This is so because a light-shielding pattern for pupil division is formed in the pixel for focus detection, and thus the amount of light entering the photoelectric conversion portion of the pixel for focus detection is small, as compared with the pixel for imaging. Since the amount of electric charge moving to an adjacent pixel depends on the amount of generated electric charge, for example, the amount of electric charge moving from the pixel for focus detection to an adjacent green pixel becomes smaller than that of electric charge moving from the red pixel to an adjacent green pixel. Thus, in the arrangement in which the pixels for imaging and the pixels for focus detection are arranged on a single substrate, the amount of crosstalk in the region where the pixel for focus detection is arranged differs from that in other regions, and this may impair the quality of an image to be obtained.